I would talk to BAT and Theta to see if the frequency can be changed.
I've owned the SLP 98, BAT 31SE, and BAT 51SE. All are wonderful and very different. The 51SE is spectacular but at a much higher pricing point. The 98 is a great preamp for the money, and I've owned it twice!
I've also worked with both Cary and BAT customer service and both are at the top of the heap for audio companies. BAT really went out of its way on a problem i had in shipping a preamp I sold. Highly recommend them.
I've owned the SLP 98, BAT 31SE, and BAT 51SE. All are wonderful and very different. The 51SE is spectacular but at a much higher pricing point. The 98 is a great preamp for the money, and I've owned it twice!
I've also worked with both Cary and BAT customer service and both are at the top of the heap for audio companies. BAT really went out of its way on a problem i had in shipping a preamp I sold. Highly recommend them.